Shelf unit



FIG. 1 is a perspective view of a shelf unit showing our new design;

FIG. 2 is a right side view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof. "

The broken lines are for environmental purposes only and form no part of the claimed design". 

The ornamental design for a shelf unit, as shown and described. 